Fuel handling and firing system



June 13, 1950 D. v. SHERBAN 2,511,017

FUEL HANDLING AND FIRING SYSTEM Filed March 15, 1944 4 Sheets-Sheet l'(I/Illlll. I' III Danz'e/ VJberba n A YTORNE Y 4 Sheets-Sheet 2 D. V.SHERBAN- FUEL HANDLING AND FIRING SYSTEM June 13,1950

Filed March 15, 1944 mmvroa Daniel I/Jberban 4 TTOIYVIL'Y Fig.3

June 13 1950 D. v. SHERBAN mar. HANDLING AND FIRING sys'mu 4Sheets-Sheet 3 Filed March 15, 1944 I uvwszvron.

Daniel Vcfberban A TTORNE Y Patented June 13, 1950 FUEL HANDLING FIRINGSYSTEM Daniel V. Shel-ban, Keyport, N. J., assignor to The Babcock &Wilcox Company, Rocklelgli, N. J a corporation of New J erscyApplication March 15, 1944, Serial No. 526,612

1 24 Claims.

The invention herein disclosed relates to a fuel handling and firingsystem particularly applicable to the treatment of blast furnace slagaccording to known fuming processes.

One such process involves the recovery of zinc and lead from blastfurnace slag in the form of zinc oxide and lead oxide, the slag from alead smelter for example being charged directly into a fuming furnace ina mclted state, and pulverized coal and combustion air introduced intothe bath at a level of approximately three feet or' more below its uppersurface. The slag is treated in batches and for each batch there is aninitial heating period during which 100 percent of combustion air isinjected with pulverized coal into the slag bath until the temperatureis elevated to the metallic zinc vaporizing temperature. At this point,the total air for combustion is reduced below 100 per cent, thusproducing a highly reducing atmosphere within the furnace reaction zoneto effect the reduction of the zinc oxide contained in the slag bath.The metallic zinc is released as a vapor that rises rapidly to emergefrom the slag and becomes reoxidized above the slag bath where a furthersupply of air is introduced. The net thermal effect of the reaction thusinvolved is equivalent to complete oxidation of the carbon in the fuel.Lead oxide in the slag is volatilized at the temperature of the slag andleaves the bath also as an oxide.

At the end of the complete operating cycle, which is determined by thediminishing rate of metal elimination from the bath, the treated slag istapped off and the furnace again charged with a fresh supply of slag forrepetition of the recovery operation.

The introduction 'of the. coalair mixture below the slag levelnecessarily requires operation of the fuel firing system underconsiderable pressure, which for the maximum operating slag level mayamount to pounds per square inch or thereabout. The pressure in thesystem may be suitably adjusted however to compensate for any changes inslag head that might occur, as during the charging and tapping periodswhich total about twenty-five percent of the complete operating cycle.

In a direct-fired system, that is, with the pulverized coal and primaryair being supplied to the burners direct from the pulverizer, withoutintervening bins or storage receptacles for the pulverized coal, itfollows that the pulverizer and its associated raw coal feedingapparatus must be maintained under pressures higher than those requiredat the burner outlets.

The adaptation of direct-firing to the fuming process has accordinglypresented problems for which the present invention provides a desirablesolution.

An object of the invention therefore pertains to a direct firedpulverized coal system wherein the pulverizer and its accompanyingfeeder apparatus may be maintained at internal operating pressures inexcess of those heretofore employed.

An additional object resides in maintaining the pulverizer and feederunder unusually high operating pressure conditions while providing for.regular admission of raw coal to the feeder to maintain the desired rateof pulverizer output.

A further object is directed to a suitable charging system for thepulverizer feeder whereby, raw

' coal may be supplied continuously to the pulverizer feeder withoutloss of operating pressure from within the pulverizing apparatus.

Other objects provide for a charging apparatus formed in two portions,whereby raw coal delivered to one portion intermittently from an outsidesource is transferred to a second portion for continuous delivery to thepulverizing apparatus.

26 More specific objects include the coordination of coal flow into thecharging apparatus with coal flow through and from the chargingapparatus; the appropriate sequence and cycle of valving operations toestablish and maintain pressures in various parts of the system at theirpredetermined operating values; together with distributor meansparticularly adapted for direct-firing service in a metalrecoveryprocess requiring distribution of fuel and air to a plurality ofburners for injection throughout a molten mass of metal containingmaterial.

The foregoing and other objects and features of the invention will bemore fully recognized lected embodiment of the invention as illustratedin the accompanying drawings, wherein,:,,

Fig. 1 is an elevational outline of apparatus ar ranged in accordancewith my invention for continuous firing of pulverized coal under highpressure conditions;

Fig. 2 is a plan view of a portion of the syste illustrated in Fig. l,the coal handling apparatus preceding the pulverizer feeder beingomittedi e Fig. 3 is a sectional elevation of the raw 'i'coal chargingapparatus of Fig. 1 together withassociated valve control elements:

Fig. 4 is an enlarged fragment of Fig. 3;

Fig. 5 to Fig.- 8 inclusive are diagrammaticsec- 55 tlonal viewsillustrating the cycle of operations from the ensuing descriptionpredicated on a se-- involved in the handling of raw coal prior toentering the pulverizer feeder;

Fig. 9 is a diagram of the electrical circuits involved in the automaticcontrol of the system disclosed; and

Fig. 10 is a longitudinal section of a specific conduit element includedin Figs. 1 and 2.

Figs. 1 and 2 illustrate an embodiment of my invention in a system forrecovering metals from blast furnace slag in accordance with knownprinciples of slag fuming practice. In the arrangement shown, the slagto be treated is charged into a fuming furnace 20 which is provided witha series of tuyere burners 22 distributed along two of its oppositesides; each burner projecting a mixture of pulverized coal and air intothe bed of slag at the bottom of the furnace whereby the slag isrendered molten and maintained molten by the heat of combustion of thefuel, while a suitable reducing atmosphere is maintained throughout themolten bath to effect the desired reaction.

The mixture of fuel and air projected into the furnace 20 throughburners 22 includes a mixture of pulverized coal and primary airdischarged under pressure from an air swept pulverizer 24 andtransported direct to each group of burners through the burner lines 20and 28 respectively; each burner line 20 or 2. being connected to adistributing header :2 through a transition piece SI and nozzle II bywhich the mixture is discharged tangentially and uniformly along theentire length of the header. Burner pipes 34 extend downwardly from thebottom of each header at longitudinal spacings to provide connections toindividual burners 22; each burner pipe 84 being suitably povided with ashut off valve 30. Additional or secondary air for burners 22 issupplied under pressure through secondary air pipes 88 leading from amanifold ll having a conduit connection 42 with a suitable course, notshown.

Each transition piece ll, as detailed in Fig. 10, is formed as a conduitelement having an inlet 20 of circular cross section corresponding tothe circular cross section of burner line 28 or 28, and having an outlet33 in the form of a narrow rectangular opening corresponding to the rectangular cross section at the entrance of nomle 3|. Flanges I! and 31maybe provided at opposite ends of each transition piece for connectiondo the burner lines 20 and 2|. and to nozzles 3|; each nozzle forming anintegral part of each header I2, if desired. Intermediate flanges 39 andribs ll constitute reinforcing members. The internal cross sectionalarea of an element 30 is practically the same at both ends, although theelement is of gradually flaring formation in a horizontal direction sothat its outlet extends from one end of the header 82 to the others:

theinternal diameter of a distributing header 82 being approximatelytwice the diameter of the inlet opening 2!. The nozzle ll, of the samein ternal crm section as theoutlet 33 of element 30,

is arranged tangentially of the header 32 to cause the entering fuel andair to sweep the' inner wall of the header along its entire length,thereby to minimize pressure drop at relatively high flow velocities.Tests on apparatus proportioned substantially as above described andconstructed for commercial service have shown that with an entrancevelocity through inlet 2! of 4000 feet per minute, the pressure dropthrough the entire distributor from inlet 29 to the entrances to thepulverizer by means of a feeder of any suitable type; the feeder shownbeing of a known type of mechanical feeder 46 having a two-speedelectric motor drive 48, independent of the pulverizer drive 44, forcontrolling the input of coal to the pulverizer in accordance with thedesired output requirements. The feeder I! is supplied continuously withraw coal from a multichamber charging system 54 through a feed spout Illfitted with a shut-off valve 52.

Primary air at the required pressure is supplied to the pulverizerthrough the primary air pipe It, the 'air constituting a gaseous carriermedium for conveying flnely divided coal particles through and from thepulverizer to provide a fluent output mixture of pulverized coal and airfor delivery through the burner lines 20 and 28. In the systemdescribed, the pulverizer II is operated at relatively high internalpressures since an appreciable resistance must be overcome at theoutlets of burners 22, due to the bed of slag in the furnace 20; anormal operating value being about ten pounds per square inch maximum,although operation may be successfully carried out at considerablyhigher pressures depending on the amount of back pressure to beencountered. The primary air is preferably preheated to an extentenabling the temperature of the output mixture to be maintained constantat approximately 150' F.

Raw coal is supplied to the pulverizer charging system II from anelevated storage hopper II, the coal being weighed by a scale device Illknown as a weightometer from which the coal passes -to a belt conveyor02 and into the feed spout or hopper 0| for discharge into the top endof an upper charging bin, or feeder bin 80. The conveyor 82 may be oerated continuously or intermittently: in the latter instance its oeration being interlocked with the operation of the scale 80. as in thepresent system. As shown in Fig. 3, a bell valve or gate Cl ispositioned at the lower end of the feed hopper N for controlling themovement of coal from the feed hopper to the chamber 10 provided withinthe upper charging bin 80, a bell valve or gate 12 being positioned atthe lower end of the upper charging bin 00 for controlling the movementof coal from the char in: chamber II to the chamber 14 provided withinthe lower charging bin, or supply vessel It.

The top gate 88 is secured to a hollow rod or tube I8 actuated bv thepiston of the air cylinder 82, the rod 18 extending through both ends ofthe cylinder and being movable longitudinally in a lower guide bearing84; the bottom gate 12 being secured to a rod 86 telescoping within thehollow rod 18 and actuated by the piston 8| of the air cylinder". Eachgate when in its closed position is resiliently seated against a flanged7 rubber ring 92 to afford an effective seal for the respective chargingchambers I8 and 14 against an internal working pressure of about 10 p.s. i. at various stages of the bin charging cycle.

The opening and closing movements of gates .68 and I2 are controlled bythe four-way electrically operated valves 94 and 96 respectively havingconnections 98 and I88 with a supply line I82 carrying air or othersuitable fluid under pressure; such valves being shown diagrammaticallyin Figs. 5 to 8 inclusive; a fluid pressure of approximately 40 p. s. i.being generally suitable for the purpose.

Valve 94 for controlling the operation of the upper gate 68 is connectedto the cylinder 82 by lines I84 and I86 at opposite sides of the piston88; valve 96 for controlling the operation of the lower gate I2 beingconnected to the cylinder 98 by lines I88 and H8 at opposite sides ofthe piston 88. Valve 84 is formed with internal passages II2 and H4, andvalve 96 with similar in ternal passages H6 and H8, for admitting fluidunder pressure to the cylinders at either side of their respectivepistons 88 and 88, and for simultaneously exhausting fluid from thecylinders at the opposite sides of the respective pistons.

For example, in order to cause the upper gate 88 to be moved downwardlyto its open position, as indicated in Fig. 5, the passage II2 of valve84 is brought into register with the supply line connection 98 andcylinder connection I84, while the passage H4 is brought into registerwith the cylinder connection I88 and the exhaust port I28, therebyestablishing a higher pressure above than below the piston 88 andcausing the upper gate 88 to be opened. In order to return the uppergate 68 to its closed position, as indicated in Fig. 6, the valve 94 isoperated to transpose the positions and corresponding connections of.the internal passages H2 and H4, thereby establishing a higherpre'ssure'below the piston 88 than above; the passage II4 connecting thesupply line connection 98 with the cylinder connection I88, and thepassage II2 connecting the cylinder connection I84 with the exhaust portI28. The lower gate I2 is opened and closedv in a similar manner, as isevident from the drawings; valve 96 being operated to position thepassage H6 and H8 as shown in Fig. 6 to cause the gate I2 to be opened,and as shown in Fig. 5 to cause the gate I2 to be closed.

An electrically operated three-way valve I22 is provided to regulatefluid pressure conditions within the upper and lower bin chambers 18 andI4; the valve I22 having connections I24 and I26 with the bins 66 and I6respectively, and having an internal passage I28 for connecting theupper bin connection I24 either with the lower bin connection I26 forequalizing pressures between the bin chambers I8 and I4, or with theexhaust port I88 for venting the upper bin chamber I8. If desired, thepressures in bin chambers I8 and I4 may be equalized by providingconnections for the three-way valve I22 as shown in Fig. 3, whereby bothchambers may be connected to a common fluid pressure source such as theprimary air duct 56 leading to the pulverizer; the connection I26 fromthe valve I 22 direct to the lower bin I8 being replaced by the two airduct connections I 82 and I33 leading from the valve I22 and the bin I6respectively.

When equalization is efl'ected by the connections shown in Figs. 5-8,the resulting pressure above the bed of coal is due only to filtrationand therefore lower than the pressure within the pulverizer, which ifthe diflerentiai were high enough might interfere with the feed of coalto the pulverizer. However, when the bin pressures are equalized byproviding connections to contacts PS (Fig. 9) are closed and the systemis conditioned for opening the bottom gate I2 between the upper andlower bins 66 and I6. For another condition of the system, with the topand bottom gates closed, and when it is desired to open the top gate 68for charging theupper bin 66, the three-way valve I22 is moved to itsventing position (Fig. 5) whereupon the pressure in the upper bin 66 isreduced to atmospheric pressure causing the switch contacts PS to beopened.

The operation of the various valves (94, 96, I22) gates (68, I2), andcoal weighing and feeding devices (68, 62), is controlled by high levelindicators I35 and I36 mounted on the top and bottom bins respectively,together with limit switches I38 and I48 actuated by a bar I46 movablewith the top-gate rod I8, and limit switches I42 and I44 actuated by abar I48 movable with the bottom-gate rod 86. The bottom bin I6 may beequipped with a low level indicator I58, if desired, merely to actuatean alarm or signal, without entering into the control of the system.

The high level indicators I34 and I36 are suitably of the type disclosedin U. S. Patent 1,936,844, A. G. Kinyon. patented November 28. 1933,wherein an electrical circuit is either opened or closed in response tothe swing or deflection of a pendulous member from its normal positionof rest, each indicator incorporating an associated switch suitably ofthe Mercoid type. As shown in Fig. 3, 'the high level indicator I34 forthe too bin 66 includes a pivoted paddle member or lever I52 formed witha paddle I54 at its lower end, the indicator being mounted at such alocation as to cause the member I52 to be deflected to an extentsuffcient to close the contacts of an associated switch HLT when the bed,of coal in the upper bin 66 reaches a predetermined maximum level. Atlower levels and when the bid is empty. the lever resumes its normalpendulant position to oven the contacts of the switch. The paddle memberI52 is partially enclosed by a front plate I56 and side plates I58forming a compartment open at its bottom to prevent the incoming coalfrom bu lding up behind the paddle I54 and preventing its deflection;the paddle I 54 having its lower portion extended at an angle to thevertical, as at I68, to assure more positive deflecting action.

The high level indicator I36 forwthe bottom bin I6 includes a pivotedpaddle member or lever I62 having a paddle I64 at its lower end and anadditional paddle I66 at an intermediate location; the paddle I 86 beinginclined to the lower paddle I64 and therefore inclined to the verticaland in the path of the incoming coal from the upper bin 66. The paddlemember I62 is thus caused to be de-.- flected not only by the level ofcoal in the lower bin I6, at some predetermined maximum level, but alsoby the flow of coal intothe lower bin I6 from the upper bin 66. Thedeflection of the padauaoiv 7 die member "2 under either of these twoconditions causes the contacts of the associated switch HLB to beclosed; the return of the paddle member III to its normal pendantposition causing the contacts of the switch HLB to be opened.

The limit switches I, ll, I42 and I are mounted as shown in Figs. 3 and4 adjacent the line of travel of the top and bottom gate rods 18 and Itso as to be actuated by the respective bars I u and I which projecttherefrom. When the top gate it is moved upwardly to its closedposition, the bar I attached to the outer gate rod II is moved to itscorresponding uppermost position whereupon it engages the arm of thesnapaction switch ill to cause the associated switch contacts LST-i tobe opened; when the top gate 88 is moved downwardly to its openposition, the bar I" being moved to its corresponding lowermost positionwhereupon it engages the arm of the snap-action switch I to cause theassociated switch contacts HST-2 to be closed. Similarly, when thebottom gate 12 is moved upwardly to its closed position, the bar I"attached to the inner gate rod 86 is moved to its correspondinguppermost position whereupon it engages the arm of the snap-actionswitch "2 to cause the associated switch contacts LSB-l to be opened;when the bottom gate 12 is moved downwardly to its open position, thebar I being moved to its corresponding lowermost position whereupon itengages the arm of the snap-action switch I to cause the associatedswitch contacts 18B2 to be closed.

The cycle of operations involved in the continuous delivery of raw coalto the pulverizer feeder 4. will be understood by reference to Figs. 5to 9 inclusive; Figs. 5 to 8 being diagrammatic views of the apparatusillustrating the various positions of the control valves and bin gatesat differ-' ent stages, and Fig. 9 showing a schematic arrangement ofthe various electrical circuits for maintaining automatic operation ofthe various components throughout the cycle. In the electrical diagram(Fig. 9) the letters A and B desisnate the power terminals across whicha suitable operating voltage such as 110 volts, alternating current, maybe applied. A selector switch SW-l is included to provide for eitherautomatic" or "manual operation; the switch being shown in an "of!"position so that all circuits and windings involved are deenergized" andall switch contacts "normally open or normally closed as indicated. Itis assumed however that the pressure from line I! is on" causing bothgates I and I2 to be held closed.

The symbols VT, VB and VP designate the actuating coils or solenoids forcontrolling the operation of valves 94, 96 and I22, respectively; thecoil VT, when energized, causing the four-way valve 94 to be positionedas in Fig. to cause the top gate 68 to be opened; the coil VB, whenenergized, causing the four-way valve 98 to be positioned as in Fig. 6to cause the bottom gate 12 to be opened; and the coil VP, whenenergized, causing the three-way valve I 22 to be positioned as in Fig.6 to equalize pressures in the upper and lower bins 6t and it.

Coils HLTR. and HLBR are relay coils, for the high level indicators Iand I" respectively, which are energized or deenergized in accordancewith the make" or "break of the switch contacts HLT and HLB.

Coil PSR is a relay coil which is energized or deenergized in responseto the operation of contacts P8 of the pressure switch ill.

Coils marked "Scale and Sc. conv." are starter relay coils for motorsdrivin the scale II and scale conveyor 82 respectively.

Coils T and B are relay coils which are energized or deenergized inresponse to the operation of the limit switches I38, I40, 2 and I whosecontacts L8T--I, LST2, LSB-l and LSB-2 are opened or closed inaccordance with the opening or closing of the top and bottom gates IIand I2.

Each set of contacts which is opened or closed as the result of anygiven relay being energized or deenergized, is designated by the samesymbol as that assigned to the relay; for example, relay T at the bottomof the diagram has associated with it the contacts marked T" so thatwhen relay T is energized, all normally-closed contacts T are opened,and all normally-open contacts T are closed; and vice versa, when relayT is deenergized. In the case of the time delay relays TDRI, TDR! andTDR3, the associated contacts are identified to indicate the sequence ofoperation, if any, as in the case of relay TDRI whose contacts TDRl-land TDRI2 are operated in the order named.

Double-throw switches SW2, SW-3 and SW4 may be provided, together withthe connections shown, for manual control of individual circuits inwhole or in part; the switches being suitably arranged and interlocked,in known manner, so that only the correct sequence is possible.

The cycle of operations may be considered to start and end with thecharging of the upper bin 6 as indicated in Fig. 5. It will be assumedhowever that before the initiation of the cycle the system is in a stateof rest, with the selector switch SWI 013" as indicated in Fig. 9, andwith no coal in the system, although continuously available in thestorage bin 58. It will be further assumed that the air pressure hasbeen turned on from line I02 so that both gates. I and I2, top andbottom, are in their closed positions; with valve [22 in the ventingposition to place the upper bin I under atmospheric pressure.

The selector switch BWI may then be set for automatic" operation therebycompleting the circuit through the solenoid VT and causing the top gate88 to be opened, the contacts HLTR, PS3 and B in this circuit beingnormally closed as indicated. The opening of gate 00 results in theclosing of limit switch contacts LST--l and LST2 to complete the circuitthrough relay coil T causing the scale conveyor relay Sc. conv. to beenergized and the scale conveyor 62 to be operated. The energizatlon ofthe conveyor relay causes contacts Sc. conv. to be closed, therebyenergizing the relay marked Scale and placing the scale or weightometer6| in operation. Coal from storage bin 58 is thus weighed and deliveredto the feed spout or hopper 64 from which it passes into the uppercharging bin 66 as illustrated in Fig. 5.

When the coal in the upper bin 66 builds up to its predetermined maximumlevel, the paddle of the high level indicator I is deflected causingcontacts HLT to be closed and time delay relay TDRI to be energizedwhereupon after a predetermined interval of five seconds, for example,the contacts TDRi--l are opened, there by stopping the scale 60 whilethe scale conveyor 62 remaim in operation to empty it of coal. Abouttwenty-five seconds later, the contacts TDRl-2 are closed causing therelay HL'I'R to be energized and in addition the time delay re-' layTDR3. The energization of relay HLTR causes all contacts HLTR to beactuated, the resuit being to deenergize the starter-relay Sc. conv. tostop the scale conveyor 62, and to deenergize the solenoid VT to closethe top gate 66. The closing 01' the top gate 66 opens the limit switchcontacts IST-I and LST-2, deenergizing the relay T and restoring allcontacts T to normal, and causing solenoid V? to be energized toequalize pressures between the upper and lower bins 66 and 16. When thepressures become equalized, the pressure switch contacts PS close andrelay PSR. becomes energized to open contacts PSR, thereby holding thesolenoid VT deenergized and the top gate closed. By the time binpressures are equalized, after a time delay period of about thirtyseconds, the relay TDR3 acts to close contacts TDR3 thereby energizingthe solenoid VB and opening the bottom gate 12; the limit switchcontacts LSB-I and 153-2 closing; bottom gate relay B becomingenergized; and all contacts B being changed from their normal positions.The system is now in the condition illustrated in Fig. 6 with coalflowing from the upper bin to charge the lower bin 16.

After a certain amount of coal has run out of the upper bin 66, thepaddle of the high level indicator I34 swings back to its normalpendulant position causing the switch HLT to be opened and the relayTDRI to .be deenergized. Contacts TDRI--2 then open to deenergize relaysHLTR and TDRI which, if it were not for some corrective factor, wouldresult in relay VB being deenergized to close the bottom gate 12.However, the coal flowing into the lower bin 16 causes the paddle of thehigh level indicator I36 to be deflected so that switch HLB closes andrelay TDR3 becomes energized; contacts 'I'DR2 then closing to energizerelay HLBR; and all contacts HLBR being closed from their normally-openpositions to maintain the circuit through relay VB closed, therebyholding the bottom gate I2 open with the valve I22 still in the pressureequalizing position.

When the upper bin 66 becomes empty so that flow into the lower binceases, and provided the lower bin 16 is not full, the high levelindicator I16 returns to normal and switch HLB opens, deenergizing relayTDR2 and thereby relay HLBR; the contacts HLBR thus being restored totheir normally-open positions whereupon relay VB is deenergized and thebottom gate 12 is closed. The closing of the bottom gate causes relay Bto become deenergized and all contacts 13 to be restored to normal, thusdeenergizing relay VP for reducing the pressure in the upper bin 66. Assooon as the pressure in the upper bin reaches atmospheric pressure 01'thereabout, the pressure switch contacts PS open so that relay PSR isdeenergized and contacts PSR are restored to their normally closedposition, thereby energizing the relay VT and causing the top gate 66 toopen; relay T being energized, all contacts T changed; the scaleconveyor 62 placed in operation and then the scale 66; thus completingthe cycle and bringing the system to thecondition shown in Fig. 7, withcoal entering the ubper bin 66 as in Fi at the start of the cycle.

If during any cycle the coal from bin 66 should fill the lower bin 16,at least to the level where the paddle of indicator I36 would bedeflected and remain deflected as in Fig. 8, due to a low rate ofwithdrawal through the pulverizer feeder 46, for

example, the system will come to rest with the bottom gate I2 open, thetop gate 66 closed, the bin pressures equalized, and with the scale 60and scale conveyor idle. The condition of the system is then equivalentto that described in connection with Fig. 6 except that the indicatorI36 and its switch HLB are actuated by the high coal level in the lowerbin I6 instead of by the flow of coal into the bin. A subsequentreduction in coal level below the operating range of the indicator I 36will return the indicator to its normal position with its switch HLBopen for resumption of the charging operation as in Fig. 7.

In a system such as described, a continuous supply oi' the coal or othermaterial to be pulverized is maintained in the lower bin I6 so that thepulverizer may be operated without interruption irrespective of the rateat which the material is fed from the bin into the pulverizer by meansof the feeder 46. With the upper and lower bins of different volumetriccapacities as shown, the lower bin is large enough to hold more than asingle complete charge from the upper bin 66 and thereby provide areserve of material in the lower bin in case of a temporary interruptionin the delivery of material to the lower bin such as might result froman interruption in the supply of raw material to the storage hopper 58;the upper bin 66 being of large enough capacity so that when its normalcharge is emptied into the lower bin, the amount of material thus madeavailable to the feeder 46 is sufllcient to last through at least onecomplete bin cycle with the feeder operating at maximum capacity.

Notwithstanding the intermittent charging of the upper bin atatmospheric pressure, there is no loss of pressure from within thepulverizer since the lower bin, the feeder, and the pulverizer arecontinuously sealed against atmospheric pressure, and the bin maintainedunder fluid pressure substantially the same or higher than the internalpulverizer pressure. It will be noted also that the sealing is eiIectedby means of apparatus of such form and construction as to provide freemovement of the material therethrough and to obviate the need for anunduly high head of material which with the long system of pipingrequired would have a tendency to clog or bridge in the system and leadto an interruption or irregularity in the delivery of material.

I claim:

1. A fuel handling and firing system adapted to receive coal to bepulverized at atmospheric pressure and to discharge pulverized coal andair against a burner outlet pressure above atmospherlc pressure, ofabout ten pounds per square inch, for example, said system comprising apulverizer, a mechanical feeder opening into said pulverizer, means forforcing air through said pulverizer at a pressure suflicient to overcomesaid outlet pressure, and apparatus for continuously supplying coal tosaid feeder, said apparatus comprising an upper and a lower charging binhaving a connection therebetween for gravity flow of coal from one binto the other, said upper bin having a top coal inlet, said lower binhaving a bottom coal outlet to said feeder, a charging gate movable toopen and close the connection between said bins, a second charging gatemovable to open and close said top coal inlet, and means responsive tothe flow of coal through said apparatus for operating said charginggates in predetermined sequence to successively charge said bins whilemaintaining predetermined pressure conditions in said pulverizer.

ll 2. A fuel handling and firing system adapted to receive ,coal to bepulverized at atmospheric pressure and to discharge pulverized coal andair against a pressure equivalent to a head of molten slag or the'like,said system comprising a pul-,

verizer, a mechanical feeder opening into said pulverizer, means forforcing air through said pulverizer at a pressure suiilcient to overcomethe pressure comparable to said head of slag, and apparatus forcontinuously supplying coal to said feeder while maintainingpredetermined pressure conditions within said pulverizer, said apparatuscomprising an upper and a lower charging bin having a connectiontherebetween for gravity flow of coal from one bin to the other, saidlower bin having a bottom outlet to said feeder, means for closing saidconnection when charging said upper bin, means for equalizing pressuresbetween said bins after said upper bin has been charged, and meansresponsive to the operation of said pressure equalizing means foropening said connection between said bins.

3. A charging system for a pulverizer under a positive pressurecomprising a mechanical feeder opening into the pulverizer, a closed binarranged to discharge into said feeder, a charging hopper having amaterial inlet at its upperend and its lower end opening into said bin,a charging gate movable to open and close the connection between saidhopper and bin, a second charging gate movable to open and close saidmaterial inlet, a threeway pressure equalizing valve connected to saidhopper and bin and to the atmosphere, a material level indicator in saidbin, a second material level indicator in said hopper, and means foroperating said charging gates and pressure equalizing valve in apredetermined sequence in response to the operation of said levelindicators to successively charge said hopper and bin while maintainingpredetermined pressure conditions in said bin and feeder.

4. A charging system for a pulverizer under a positive pressurecomprising a mechanical feeder opening into the pulverizer, a closed binarranged to discharge into said feeder, a charging hopper having amaterial inlet at its upper end and its lower end opening into said bin,a charging gate movable to open and close the connection between saidhopper and bin, a second charging gate movable to open and close saidmaterial inlet, a threeway pressure equalizing valve connected to saidhopper and bin and to the atmosphere, a material level indicator in saidbin, 8, second material level indicator in said hopper, and means foroperating said charging gates and pressure equalizing valve in apredetermined sequence in response to the operation of said levelindicators to successively charge said hopper and bin while maintainingpredetermined pressure conditions in said bin and feeder, said materiallevel indicator in said bin being additionally responsive to the flow ofmaterial into said bin. 7

5. Acharging system for anairswept pulverizer arranged to dischargepulverized material and air against a pressure equivalent to a head ofmolten slag or the like, said pulverizer having its material inletseparate from its inlet for carrier air, said system comprising amechanical feeder opening into said pulverizer for controlling the inputof material to said pulverizer through 'said material inlet, meansconnected to said air inlet for forcing carrier air through saidpulveriser at a pressure suflicient to overcome the resistance aifordedby said head of slag. a closed said feeder, an upper bin having amaterial inlet at its upper end and having a bottom connection with saidlower bin, a charging gate movable to open and close the connectionbetween said bins, a second charging gate movable to open and close saidmaterial inlet, a, pressure equalizing valve connected to said upper binand to the atmosphere, said valve and lower bin having equalizingconnections with a common source of fluid pressure substantially equalto the pressure of air supplied to said pulverizer, said valve in oneposition completing a connection between said upper bin and theatmosphere and in another position completing a connection between saidupper bin and said common source of fluid pressure, and means foroperating said charging gates and pressure equalizing valve inpredetermined sequence to successively charge said bins whilemaintaining predetermined pressure conditions in said pulverizer.

6. In a pulverizer system including a pulverizer arranged for wide rangeoperation under positive fluid pressure, apparatus for supplyingmaterial to be pulverized to said pulverizer without loss of saidpulverizer pressure comprising an inlet and an outlet chamber connectedin series, means for intermittently charging said inlet chamber atatmospheric pressure, means for intermittently charging said outletchamber from said inlet chamber at a pressure higher than atmosphericpressure, means for feeding material from said outlet chamber into saidpulverizer atsaid higher pressure apparatus in each of said chambersoperable in response to the level of material therein, and meansincluding said level responsive apparatus for restricting the operationof said charging means to a predetermined sequence and at varying rates.

7. In a system for delivering material to a pulverizer arranged to beswept internally by a gaseous carrier medium under positive pressure, acharging apparatus formed with upper and lower compartments having aconnecting passageway therebetween for gravity flow of material 'fromone compartment to the other, said upper compartment having a topmaterial inlet, a top gate for opening and closing said inlet, a bottomgate for opening and closing said passageway, means for conveyingmaterial to said inlet from a-source outside said system, means forseparately operating said conveying means and said gates, meansresponsive to the opening of said top gate for initiating the operationof said conveying means and thereby the delivery of material into saidupper compartment, means responsive to the delivery of material intosaid upper compartment for opening said bottom gate to allow material topass into said lower compartment, and means for feeding material fromsaid lower compartment into said pulverizer without loss of saidpulverizer pressure.

B. A charging system for a pulverizer arranged for operation underpositive fluid pressure comprising a means for feeding material intosaid pulverizer at varying rates, an upper and a lower bin having aconnection therebetween for gravity flow of material from one bin to theother, said upper bin having a material inlet at its top end, said lowerbin having a material outlet at its bottom end continuously open to saidfeeding means, a top gate for opening and closing said material inletand a bottom gate for opening and closing said connection, means foroperating each of said gates, a conveyor for delivering material lowerbin arranged for gravity discharge intotosaidmaterialinletatatmosphericpressuraa weighing device, means forclosing said top gate when the material in the upper bin reaches apredetermined level, means for equalizing the fluid pressures in saidbins and thereafter openving said bottom gate while holding said topgate closed to allow material to flow into said lower bin for feedinginto the pulverizer, and means for closing said bottom gate upon thecessation of material flow into said lower bin.

9. In a system for delivering material to a pulverizer arranged to beswept internally by a gaseous carrier medium under positive pressure, acharging apparatus formed with upper and lower compartments having aconnecting passageway therebetween for gravity flow of material from onecompartment to the other, said upper compartment having a top materialinlet, said lower compartment having a bottom material outlet, means fortransferring material from said outlet into said pulverizer without lossof said pulverizer pressure, a top gate for opening and closing saidinlet, a bottom gate for opening and closing said passageway, a scalefor .weighing material passing therethrough, means including said scalefor conveying weighed amounts of material to said inlet from a sourceoutside said system, means for operating said conveying means and saidgates in predetermined sequence to hold said bottom gate closed and saidtop gate open during the operation of said conveying means, and meansresponsive to a predetermined increase in level of material in saidupper compartment for interrupting the operation of said conveying meansand for subsequently closing said top gate while continuing to hold saidbottom gate closed.

10. In a pulverizer system including a pulverizer arranged to be sweptinternally by a gaseous carrier medium under superatmospheric pressure,said pulverizer having an inlet for material to be pulverized separatefrom the inlet for said gaseous medium and having an outlet for saidgaseous medium together with pulverized material entrained therein, asuperposed supply receptacle under atmospheric pressure for material tobe pulverized, a regulating feeder discharging into the pulverizer andthereby having its outlet subject to the pressure within saidpulverizer,and means intermediate said receptacle and said feeder for transferringmaterial from said receptacle to the intake of said feeder by gravity,said means being constructed. and arranged to restrict the loss ofpulverizer pressure by restricting the escape of said gaseous medium incontraflow relation to the discharge of material into said pulverizer,said means comprising an upper chamber and a lower chamber connected inseries in gas tight relationship, said upp chamber being arranged toreceive material from said receptacle and said lower chamber having anoutlet continuously open to the intake of said feeder, and meansresponsive to changes in material levels within said chambers forregulating material flow into and from said upper chamber, said lastnamed means including valving means between said receptacle and saidupper chamber and between said upper and lower chambers.

11. In combination with a pulverizer arranged to be swept internally bya gaseous carrier medium under superatmospheric pressure, said puiverizer having an inlet for material to be pulverized and a separateinlet for said carrier medium, a feeder connected tosaid material inletfor supplying material to said pulverizer at regulable rates, apparatusfor receiving material to be pulverized from a source of supply atatmosphericpressure and for delivering said material to the intake ofsaid feeder at a pressure corresponding to the pressure within saidpulverizer. said apparatus comprising an upper chamber and a lowerchamber arranged for gravitational flow of material therethrough andinto said feeder, means for alternately charging said upper chamber withmaterial from said source and said lower chamber with material from saidupper chamber. said lower chamber having a charging capacity greaterthan the charging capacity of said upper chamber, and means responsiveto the movement of material through said chambers for controlling thefrequency of saidalternate charging operations.

12. In a direct firing pulverizer system wherein fuel is projected intoa furnace in a pulverized state for combustion within a mass of materialsuch as blast furnace slag, the method of handling said fuel fordeliveryinto said furnace at a pressure sufficient to overcome theresistance due to said mass, which comprises, transferring said fuel inan unground state from a source at atmospheric pressure into apulverizing zone swept by a gaseous medium under superatmosphericpressure while restricting the escape of said medium from saidpulverizing zone other than the normal discharge through the pulverizingzone outlet, transporting pulverized fuel from said pulverizing zoneoutlet in a stream of said carrier medium, conducting said streamcontaining said pulverized fuel direct to said furnace, and maintainingsaid carrier medium at a pressure sufficient to deliver said pulverizedfuel into said furnace against the resistance afiorded by said mass.

13. A fuel handling and firing system adapted to receive coal to bepulverized from a source at atmospheric pressure and to dischargepulverized coal and air against a superatmospheric pressure equivalentto a head of molten slag or the like, said system comprising apulverizer having an inlet for coal to be pulverized and a separateinlet for carrier air, a feeder connected to said coal inlet fordelivering unpulverized coal into said pulverizer, means connected tosaid air inlet for forcing air through said pulverizer for dischargetherefrom together with pulverizedcoal carried by said air at a pressuresufllcient to overcome the pressure comparable to said head of slag,andapparatus including said feeder for continuously supplyingunpulverized coal to said pulverizer without affecting pressureconditions within said pulverizer.

14. The method of supplying pulverized fuel to a combustion chamber forcombustion therein under a pressure at least several pounds per squareinch above atmospheric pressure which comprises, transferring the fuelin an unpulverized state from a source at atmospheric pressure through aseries of zones into a final pulverizing zone in which asuperatmospheric pressure above the combustion chamber pressure ismaintained, intermittently .maintaining the first of said zones atatmospheric ceeding zones including said pulverizing zone, di-

recting a gaseous carrier medium through said pulverizing zone forcontinuous transportation of pulverized fuel thereby from said zone andthe maintenance of said superatmospheric pressure therein, andconducting said pulverized fuel and carrier medium direct to saidcombustion chamber.

15. In a direct firing pulverizer system, an air swept pulverizer havinga discharge connection to a furnace zone adapted to receive pulverizedfuel at superatmospheric pressures ranging upwardly to at least p. s.i., said pulverizer being of a mechanical type having relatively movablegrinding surface components and having an inlet for raw fuel and aseparate inlet for carrier air by which pulverized fuel is transportedto said furnace zone, an air supply conduit conducting carrier air tosaid pulverizer air inlet at positive pressures higher than the pressurein said furnace zone, a raw fuel charging chamber system for saidpulverizer comprising a superposed charging bin having a bottom outletfor gravity discharge of fuel therefrom, a mechanical feeder connectingsaid bottom fuel outlet to said pulverizer fuel inlet for regulating thedelivery of raw fuel into said pulverizer, and means for maintainingsaid charging bin under positive pressure comprising a valve oppositesaid outlet and an air pressure connection to said air supply conduit.

16. A charging system for a pulverizer internally swept by gaseouscarrier fluid under positive pressure and having conduit meansassociated therewith for supplying said carrier fluid thereto, saidcharging system comprising a mechanical feeder opening into thepulverizer, a closed bin arranged to discharge into said feeder, acharging hopper having a material inlet at its upper end and its loweropening into said bin, a charging gate movable to open and close theconnection between said hopper and bin, 9. second charging gate movableto open and close said material inlet, pressure equalizing means havingfluid connections with said bin and said hopper respectively and withsaid conduit means supplying carrier fluid to said pulverizer, a valvein said hopper' connection operable from a pressure equalizing positionto a position providing a connection from said hopper to atmosphere, amaterial level indicator in said bin, a second material level indicatorin said hopper, and means for operating said chargin gates and saidvalve in a predetermined sequence in response to the operation of saidlevel indicators to successively charge said hopper and bin whilemaintaining predetermined pressure conditions in said bin and feeder.

17. In combination with a pulverizer arranged to be swept internally bya gaseous carrier medium under superatmospherie pressure. saidpulverizer having an inlet for material to be pulverized and a separateinlet for said carrier medium, a feeder connected to said material inletfor supplying material to said pulverizer at regulable rates, apparatusfor receiving material to be pulverized from a source of supply atatmospheric pressure and for delivering said material to the intake ofsaid feeder at a pressure corresponding to the pressure within saidpulverizer, said apparatus comprising an upper chamber and a lowerchamber arranged for gravitational flow of material therethrough andinto said feeder, means for intermittently charging said upper chamberwith material from said source and said lower chamber with material fromsaid upper chamber, means in one of said chambers responsive in part tothe flow of material into said one chamber and in part to the level ofmaterial within said one chamber, and means including said last namedmeans for maintaining a predetermined sequence of said intermittentcharging operations while maintaining predetermined superatmosphericpressure conditions within said pulverizer.

18. In combination, an air swept pulverizer. a closed supply vessel forraw fuel having an open feeding connection with the pulverizer, a closedfeeder bin for the supply vessel having a filling opening and having agravity flow outlet to the supply vessel, a source 01 operating airunder pressure connected with the pulverizer for delivery of fueltherein to a furnace, an air pressure equalizing line from the source ofoperat ing air to the feeder bin, a normally open air valve in said lineoperable to close the line and connect the bin with atmosphericpressure, a closure valve for the filling opening of the feeder bin, aclosure valve for the outlet of the feeder bin, means operable by a riseof material in the supply bin to a predetermined level to cause theclosure valve in the outlet of the feeder bin to move to closedposition, means operated by the closing of said valve to adjust the airvalve in the pressure equalizing line to connect the bin withatmospheric pressure, means in the feeder bin operable by such change ofair pressure in the bin to open the closure valve of the filling openingof the feeder bin, means operable by a rise of material in the feederbin to a predetermined level to move the closure valve of the fillingopening of the feeder bin to closed position and means operable incidentto the closing of said valve for moving the closure valve of the outletopening of the feeder bin leading to the inlet of the supply vessel toopen position and to adjust the air valve of the pressure equalizingline to normal position.

19. In combination, an air swept pulverizer, a source of operating airconnected with the pulverizer, a closed supply vessel for raw fuelhaving a gravity feed connection with the pulverizer, a closed feederbin having a fllling opening and having a gravity flow discharge passageinto the supply vessel, an air pressure equalizing line from the sourceof operating air to the feeder bin, a valve in said line operable toselectively connect the bin with atmospheric pressure or with thepressure of operating air, a closure valve for the filling opening ofthe feeder bin, a closure valve for the discharge passage into thesupply vessel. an air pressure switch and a high level indicator switchin the feeder bin, a high level indicator switch in the supply vessel,devices operating under control of said high level indicator switch ofthe supply vessel to close the valve in said discharge passage, devicesoperated incident to such movement of said valve to open the valve inthe pressure equalizer line to effect a condition of atmosphericpressure in the feeder bin, devices energized by the said pressureswitch incident to this condition of atmospheric pressure, to open thevalve in the fllling opening of the feeder bin for delivery of raw fuelinto the feeder bin, devices controlled by actuation of the high levelindicator in the feeder bin for closing the said closure valve of thefeeder bin, devices operated incident to closing of said closure valveto cause the valve in the pressure equalizing line to be adjusted toadmit operating air pressure to the feeder bin, devices operated by theair pressure switch when air pressure in the feeder bin equals 17 thatin the supply vessel, to cause the valve in the discharge opening of thefeeder bin to be opened.

20. A combination as recited in claim 19 wherein the control devices forthe valves of the said filling opening and discharge passage of thefeeder bin are connected with pistons in double acting pressurecylinders, and each of said cylinders is connected at its ends with asource of pressure medium through a. four-way solenoid valve; theclosure valve for the discharge passage of the feeder bin being closedby an'energizing circuit that is controlled through the high levelindicator switch of the supply vessel and the closure valve for thefilling opening of the feeder bin being closed through the said airpressure switch.

21. A combination as recited in claim 19 wherein the control devices forthe valves of the feed filling opening and discharge passage of the 20feeder bin are connected with pistons in double acting pressurecylinders and each of said cylinders is connected at its ends with asource of pressure medium through a four-way solenoid valve, the closurevalve for the discharge passage of the feeder bin being opened by anenergizing circuit that is controlled by the high pressure limit of theair pressure switch in the feeder bin, and the closure valve for thefilling opening of the feeder bin being opened by the low pressure limitof the air pressure switch.

22. In combination, an air swept pulverizer, a source of operating airunder pressure, connected with the pulverizer for the forced delivery ofpulverized fuel therefrom to a point of use, a closed 36 ,7 7, 4

pressure equalizing line from the source of operating air direct to thefeeder bin, closure valves for the filling opening of the feeder bin,and for its outlet, high level control means in the supply bin to closethe latter valve, and means operable by the closing of said valve toclose the air pressure equalizing line and connect the bin withatmospheric pressure, means in the feeder bin operable by such reductionin air pressure to open the valve of'the filling opening of thefeederbin, high level means in the feeder bin to move its closure valveto closed position, and means operable by such closing movement to openthe outlet valve to the supply vessel.

23. A combination as recited'in claim 22 including a normally inactivemeans for feeding 579-804 18 raw fuel to the filling opening of thefeeder bin, means operable incident to the opening of the closure valvefor the fillin opening of the bin to activate the feeding means andoperable incident to the closure of said valve to deactivate the saidfuel feeding means.

24. In combination with material-using'apparatus operating underpositive fluid pressure, a charging system for supplying material tosaid apparatus without loss of said apparatus pressure comprising aninlet and an outlet chamber connected in series, means forintermittently charging said inlet chamber at atmospheric pressure,means for intermittently charging said outlet chamber from said inletchamber at a pressure higher than atmospheric pressure, means fordischarging material from said outlet chamber into said material-usingapparatus at said higher pressure, apparatus in an upper portion of atleast one of said chambers operable in response to the level of materialtherein, and means including said level responsive apparatus forcontrolling the sequence of said intermittent charging operations.

DANIEL V. SHERBAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 960,857 Eggert Jan. 7, 19101,439,957 Garred Dec. 26, 1922 Jacques May 6, 1930 1,846,826 Anderson eta1 Feb. 23, 1932 1,882,056 Bailey Oct. 11, 1932 1,883,218 WohlenbergOct. 18, 1932 1,894,020 Chance Jan. 10, 1933 1,897,750 Brassert Feb. 14,1933 1,9431589 Domina Jan. 16, 1934 2,012,934 Hardgrove Aug. 27, 19352,073,553 Dienst Mar. 9, 1937 2,100,848 Hardgrove Nov. 30, 19372,103,453 Graemiger Dec. 28, 1937 2,159,629 Hardgrove et a1. May 23,1939 2,222,030 Hague Nov. 19, 1940 2,226,923 Cross Dec. 31, 19402,338,606 Voorhees Jan. 4, 1944 2,375,057 Wiegand May 1, 1945 2,387,548Wiegand Oct. 23, 1945 FOREIGN PATENTS Number Country Date France Oct.24, 1924

